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Physiology > Exam 4 Pulmonary > Flashcards

Exam 4 Pulmonary Flashcards

1
Q

Describe the 2 mechanisms by which increased blood flow leads to decreased pulmonary vascular resistance.

A

distension

recruitment

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2
Q

Name the principle stimulus for pulmonary vasoconstriction.

A

hypoxia (low O2 in tissues)

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3
Q

Distinguish between passive and active contributors to pulmonary vascular resistance, and list principle vasoactive mediators along with their effects (i.e. constriction vs. dilation).

A

passive:
- distension and recruitment (decrease PVR)
- lung volume (low, high, FRC)

active:
- hypoxic pulmonary vasoconstriction (alveolar hypoxia) due to

vasoactive mediators
- ACh, histamine, leukotrienes (bronchoconstriction)
- E/NE, nitric oxide (bronchodilation)

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4
Q

Name 2 fundamental causes of pulmonary hypertension.

A
  1. increased pressure pulmonary arteries
  2. increased PVR
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5
Q

Define each of the 3 major categories of receptors, and give examples of each (i.e. location of receptor, stimulus, end result).

A

central chemoreceptors: medulla, respond, changes in H+
peripheral chemoreceptors: aortic and carotid body, changes in H+ and PaO2
spindle stretch receptors: diaphragm, intercostal m., respond to elongation of muscle during breath
pulmonary stretch receptors: tracheal and bronchial smooth m, lung stretch/airway deformation
pulmonary irritant receptor: between epithelial cells, lung distension/irritants/cold air coughing and bronchoconstriction
juxtacapillary receptors: activated with increase interstitial fluid & capillary pressure to cause tachypnea and sensation of dyspnea

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6
Q

Explain why individuals residing at altitude have a more robust ventilatory response to hypercapnea.

A

increased PaCO2
people at altitude want to decrease PaCO2 and increase PaO2

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7
Q

Define the following lung volumes and capacities: TLC, TV, RV, FRC.

A

total lung capacity: total volume of air in lungs after maximal inhalation
tidal volume: volume normally inhaled or exhaled with each breath
residual volume: air remaining in lungs after max. Expiration (air “trapped” in lungs)
functional residual capacity: volume of the lungs at resting midposition/lung volume at rest

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8
Q

Define pulmonary compliance, and discuss how it is affected by lung volume.

A

relationship between volume/pressure
low lung volume = high compliance
high lung volume = low compliance

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9
Q

Define the 2 factors that contribute to lung elastic recoil, and explain why the lung and chest wall exert opposing forces.

A

collagen/elastin & surface tension

chest wall wants to pull outward whereas the lungs want to recoil

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10
Q

Discuss how a decrease in pulmonary compliance changes FRC, resting pleural pressure and change in pleural pressure during breathing.

A

FRC = RV + ERV
increase FRC
resting pleural pressure doesn’t change
change pleural pressure must be higher to expand the lung

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11
Q

Define the source and role of surfactant, and discuss the concept of surface tension as it relates to the alveoli.

A

decreases surface tension to allow lungs to inflate

type II pneumocytes

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12
Q

Using the Law of LaPlace, predict how pressure, tension and alveolar radius will change with surfactant deficiency.

A

increase pressure
increased tension
decreased radius = increase pressure
P = 2T/r

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13
Q

Define airway resistance in terms of airway radius, and in terms of the pressure/flow relationship.

A

increased pressure = increased resistance (decreased radius)

increased flow = decreased resistance (increased radius)

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14
Q

Name the 3 physiologic determinants of airway resistance?

A

diameter/radius
flow (turbulent or laminar)
velocity

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15
Q

Compare and contrast the upper vs. lower airways in terms of area, flow velocity, resistance and type of air flow.

A

upper: increased resistance, turbulent flow, high velocity, small CSA
low: decreased resistance, laminar flow, low velocity, increased CSA

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16
Q

Explain why extrathoracic airways behave differently than intrathoracic airways in relation to generation of maximal resistance, and how this is manifested clinically.

A

extrathoracic airways (e.g. trachea) more likely collapse during inspiration due to increased (-) P and increased resistance = dyspnea (difficulty/labored breathing)

intrathoracic airways (e.g. emphysema) more likely to collapse during expiration

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17
Q

Define interdependence, and discuss how this mechanism contributes to compliance and resistance.

A

alveoli next to each other are dependent on the other to remain open

increases compliance and decrease resistance

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18
Q

Define the physiologic parameter that most closely parallels the work of breathing, and list the 2 fundamental determinants of work of breathing.

A

respiratory distress

  1. elastic work (compliance)
  2. resistance work (resistance)

work will increase decreased compliance and increased resistance

19
Q

Discuss how animals with obstructive and restrictive pulmonary disease minimize the work of breathing.

A

obstructive pulmonary disease: increased airway resistance = max at high lung volume; compensation by deeper breathes for increased negative pressure

restrictive pulmonary disease: decreased lung compliance = compliance work is max at low lung volumes; compensation occurs when patients breathe small lung volumes rapidly

20
Q

Name the 4 determinants of pulmonary diffusion, and describe whether each factor is directly or inversely related to the rate of gas movement between the alveolus and blood.

A
  1. area of diffusion
  2. diffusion coefficient
  3. driving pressure (PAO2-PcO2)
  4. thickness

VO2 = DAP/x

21
Q

Describe the relationship between capillary transit time and diffusion under conditions of both rest and exercise.

A

slower velocity will result in more time for diffusion

exercises causes challenge in diffusion bc increased velocity = decreased diffusion

22
Q

Describe the effects of gravity on blood flow, ventilation and pleural pressure.

A

gravity increases blood flow at the base of the lungs, increases ventilation at the base lungs, base of lungs has least amount of pressure

23
Q

what challenges diffusion

A

alveolar hypoxia (altitude)
exercise
thickening of blood gas barrier

24
Q

Define the 2 mechanisms that act to match ventilation to blood flow.

A
  1. collateral ventilation (dog/cat > human/horse > cows/pigs)
  2. hypoxic vasoconstriction (diverting blood to better-ventilated alveoli)
25
Q

Describe the mechanism of a shunt, particularly addressing response to supplemental oxygen and mechanism of hypoxemia.

A

shunt mixed venous and arteriole blood

large shunt but not low V/Q is relatively unresponsive to supplemental oxygen due to increase PAO2 in alveoli don’t fully compensate for hypoxemic blood

administer supplemental O2 regardless because with hypoxemia, small increases in PaO2 can improve SaO2 and CaO2

26
Q

List the 3 causes of impaired gas exchange (increased A-a gradient).

A

V/Q mismatch (physiological shunt)
anatomical shunt R –> L
diffusion impairment

27
Q

Explain why a pulmonary thromboembolism causes hypoxemia (i.e. what is the mechanism), and whether these animals respond to supplemental oxygen.

A

thromboembolism = clot in intravascular = decreased diffusion area (A) = decreased diffusion = hypoxemia

VO2 = DAP/x

they can respond to supplemental oxygen since increase PAO2 increases change in P and there is no venous admixture

28
Q

What are the TWO main* non-respiratory functions of the lung?

A

metabolic*
immunologic*
olfaction
phonation

29
Q

Name at least three enzymes/hormones that undergo degradation in the pulmonary circulation and describe how that is important.

A

ACE
monoamine oxidase
prostaglandins E2 and F2
leukotrienes
toxins

30
Q

Describe how debris and pathogens are cleared from the respiratory system.

A

specific defenses (IgA = mucus)
non-specific defenses: mucociliary system and macrophages

31
Q

Describe the meaning of the P50 of hemoglobin, and discuss the effects of species/metabolic demands, pH, temperature, PCO2 and DPG on the oxygen-hemoglobin dissociation curve.

A

P50 of Hgb: partial pressure of O2 when Hgb is saturated at 50%

P50 is good for species comparison. Elephants have low P50, small mammals have high P50 because small mammals have higher metabolic demands and requires O2 less affinity to Hgb

Hgb affinity inversely related to CO2 and acidity
- pH increases affinity increases (left shift)
- temperature increases affinity decreases (right shift)
- PCO2 increases affinity decreases (right shift)
- DPG increases affinity decreases (right shift)

32
Q

Discuss how a rightward shift in the oxygen-hemoglobin dissociation curve offers a physiologic advantage.

A

rightward shift results in unloading of O2 from Hgb due to Hgb decreased O2 affinity, offers an advantage because more O2 delivery to tissues

33
Q

Distinguish between oxygen consumption and extraction, and state the mathematical relationship between the two values.

A

O2 consumption: O2 consumed by tissues
O2 extraction: O2 used by tissues
O2 extraction = O2 consumption/delivery

34
Q

State what it is that oxygen extraction estimates.

A

amount of O2 used by tissues

35
Q

Discuss the 3 fates of CO2 once the gas leaves the tissues and diffuses into the capillary blood.

A

bicarbonate
dissolved in plasma
carbamino compounds

36
Q

Discuss how the body compensates for the following: acute hypoxemia; chronic hypoxemia; anemia; low cardiac output.

A

acute hypoxemia: increased ventilation
chronic hypoxemia: increases 2,3-BPG, erythropoiesis
anemia: increases 2,3-BPG, erythropoiesis
low cardiac output: increase cardiac output/sympathetic stimulation

37
Q

mild hypoxemia

A

PaO2 < 80 mmHg

38
Q

severe hypoxemia

A

PaO2 < 60 mmHg

39
Q

causes of alveolar hypoxia / hypoxemia

A

low FIO2 (PB)
high PaCO2 (hypoventilation)
V/Q mismatch (physio shunt)
anatomical shunt
diffusion impairment such as pneumonia, fibrosis, thromboembolism

40
Q

3 types of dead space

A

equipment dead space
physiological dead space
- anatomical
- functional

41
Q

3 factors that alter DO2

A

hypoxemia PaO2 (SaO2) = cyanosis
anemia (low Hgb)
hypotension (low CO) = heart failure, hypovolemia, dehydration, hemorrhage

42
Q

3 major systems that contribute to preservation of adequate oxygen delivery to the tissues

A

cardiovascular
erythropoietic
pulmonary

43
Q

peripheral chemoreceptors respond to

A

decreased PaO2
increased PaCO2
increased H+ (low pH)

44
Q

central chemoreceptors respond to

A

increased H+
increased CO2

Physiology (5 decks)

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